(a) Technical Field
The present invention relates to a heating control method for a fuel cell vehicle. More particularly, it relates to a heating control method for a fuel cell vehicle, in which an additional heating source, which uses waste heat of coolant of a fuel cell stack, is used together with a typical electric heater.
(b) Background Art
Internal combustion engines using fossil fuels have many problems such as environmental pollution due to exhaust gas, global warming due to carbon dioxide, respiratory diseases due to increased ozone, etc. Moreover, since the amount of fossil fuels left on earth is limited, they will be exhausted in the near future.
To address the above-described problems, various types of electric vehicles, such as a pure electric vehicle (EV) driven by a drive motor, a hybrid electric vehicle (HEV) driven by an engine and a drive motor, a fuel cell electric vehicle (FCEV) driven by a drive motor using electricity generated by a fuel cell, etc., have been developed.
In an electric vehicle, an electric heater may be used to heat the interior of the vehicle (i.e., the passenger area), unlike an internal combustion engine vehicle which is equipped with a heater that uses hot water heated by waste heat of the engine.
In particular, pure electric vehicles (which use only an electric heater), hybrid electric vehicles (which use both engine waste heat and an electric heater), and fuel cell vehicles (which use only an electric heater) are not equipped with an engine nor do they have a mode in which the engine is stopped. As such, an electric heater is necessarily required to heat the interior of these vehicles.
One example of an electric heater that is widely used is a positive temperature coefficient (PTC) heater. The PTC heater is commonly used as a heating source in a diesel vehicle together with the waste heat of the engine. Since the PTC heater can rapidly generate heat, the interior temperature can be easily increased and the heating can be easily controlled by simple control logic/means.
However, when only the PTC heater (with a maximum capacity of 5 kW, for example) is used in environmentally-friendly vehicles (e.g., pure electric vehicles, fuel cell vehicles, etc.) for heating, it is necessarily driven by and consumes the power of a battery or fuel cell. Thus, the driving distance of the vehicle is reduced.
In the fuel cell vehicle, the PTC heater is operated by the electricity generated in the fuel cell vehicle, i.e., the electricity generated by the fuel cell or the electricity of the battery charged by the power generation of the fuel cell. However, because the fuel cell vehicle is not equipped with an engine, high capacity PTC heaters are generally used, which increase the power consumed for heating the interior of the vehicle (or increases the amount of hydrogen used as a fuel), thereby reducing fuel efficiency.
Moreover, in a conventional heating system using only a high capacity PTC heater, the interior temperature can be rapidly increased, but the maximum heating performance is insufficient. Further, when the vehicle-running wind is used as air for heating in a state where a blower fan is turned off during cold conditions (e.g., in winter) when the ambient temperature is low, the temperature of the surface of the PTC heater is rapidly reduced by heat exchange with the cold outside air even when the PTC heater is operated. As a result, cold air is introduced into the interior of the vehicle.
Another example of an electric heater that has been used is a heat pump system using CO2. However, use of such heat pump systems require a significant change in the structure of the vehicle, which is problematic in terms of high cost and mass production. Moreover, high pressure conditions which are required for the application of such heat pump systems may cause a safety problem.
FIG. 1 shows an example in which a PTC heater is controlled in three stages (1 kW, 3 kW, and 5 kW) according to a change in heating load required to heat the interior of the vehicle in cold conditions (e.g., winter). In particular, the amount of heat generated by the PTC heater varies according to the variation of the heating load to maintain the interior temperature within a predetermined range.
For example, if the interior temperature does not fall within the predetermined range during operation of the heating system, the amount of heat generated by the PTC heater (with a maximum capacity of 5 kW) is increased from 1 kW to 5 kW step by step as shown in FIG. 1.
As such, when only the PTC heater is used to heat the interior of the fuel cell vehicle, in this case the fuel efficiency is significantly reduced by the power consumption of the PTC heater.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.